Optics and Fire Control

[mav1]

When did optics and Fire control get to the point when tank's have a near 100% chance hit rate at long range? What was the fist tank to be able to achieve this? How far can modern tanks fire whith a near 100% hit rate?

[John D Salt]

Originally posted by mav1:

When did optics and Fire control get to the point when tank's have a near 100% chance hit rate at long range? What was the fist tank to be able to achieve this? How far can modern tanks fire whith a near 100% hit rate?

To go into Joad mode for a minute -- that all depends on what you mean by "near" 100% and what you mean by "long" range.

Obviously, the P(hit) of all guns tends to 100% the more shots they take. The hard bit is scoring the first-shot hit. The dominating source of error for first shots has traditionally been the error in range estimation (typically 20-25% of the true distance of estimated by eye), and this explains why high-velocity guns are often thought of as "more accurate" than low-velocity ones. All else being equal, high-velocity guns tend to be less accurate, in the sense of having higher projectile dispersion at the muzzle, than lower-velocity ones, because the higher velocity requires a higher muzzle pressure. However, a relatively flat trajectory "irons out" the ranging errors much better than a relatively curved one, so the H.V. weapons tend to have higher P(hit) against targets with any height.

So my answer would be that tanks started getting long-range first-shot P(hit) with the introduction of laser rangefinders in the late 70s. By eliminating the biggest source of error, they made it worthwhile to start work on the lesser sources, and so made it worthwhile to develop the integrated digital ballistic computers and muzzle reference sensors we see today.

All the best,

John.

[MikeyD]

I just read an old report on South Africa's testing of the T72 tank (back in the days when T72s were hard to come by). Despite some ergonomic nightmares in the troop compartment the report said a T72 with a well trained crew had a pretty respectable first round hit probability at normal combat ranges. That's not what one usually hears about the T72! I guess the operative words were 'well trained' crews and 'normal' combat ranges. Out to 1500m (N.W. Europe combat ranges) the APFSDS trajectory should be as flat as a pancake.

The S.A. report also said the T72 had a pretty good stabilizer for firing on the move. Again, something not normally associated with the T72.

[dan/california]

I think that tac ops 4 has a pretty good set of hit probability tables on this subject. The verdict of virtually all recent conflicts though is that being second best, even by a little bit, will result in your being reduced to smoking wreckage in the desert. Crews and equipment both count of course.

[John D Salt]

Originally posted by MikeyD:

I just read an old report on South Africa's testing of the T72 tank (back in the days when T72s were hard to come by). Despite some ergonomic nightmares in the troop compartment the report said a T72 with a well trained crew had a pretty respectable first round hit probability at normal combat ranges. That's not what one usually hears about the T72! I guess the operative words were 'well trained' crews and 'normal' combat ranges. Out to 1500m (N.W. Europe combat ranges) the APFSDS trajectory should be as flat as a pancake.

Assuming a 3.6Kg projectile with a diameter of 41mm with a muzzle velocity of 1800 m/sec and a dispersion at the muzzle of one mil, my patent steam-powered P(hit) calculator (whose trajectory modelling may well be rubbish) gives the following percentage hit chances on a target measuring 2.5 x 2.5 metres,

...with a range estimation error of 20%:

500m__1000m__1200m__1400m__1600m__1800m__2000m

99%____75%____50%____31%____19%____12%____08%

...and with a range estimation error of 2%:

500m__1000m__1200m__1400m__1600m__1800m__2000m

99%____79%____70%____63%____57%____51%____45%

I believe that the calibre, mass and velocity figures are reasonable for a 125mm projectile, the muzzle dispersion is a SWAG but I should think of the right order.

Under these assumptions, the improvement in rangefinding essentially makes no difference up to 900m, and becomes increasingly important from then on, as you can see.

If "normal combat ranges" are 800-1000 metres, you can get by fine without a rangefinder. At 1500m, you really need it.

Originally posted by MikeyD:

The S.A. report also said the T72 had a pretty good stabilizer for firing on the move. Again, something not normally associated with the T72.

Well, it was the Russians who put the first gyro-stabilizer-equipped tank into service, was it not?

All the best,

John.

[gunnersman]

I thought the Sherman was actually the first with gyrostabilization but it was disabled by the crew because it was difficult to load while on the move or some such reason.

[John D Salt]

Originally posted by gunnersman:

I thought the Sherman was actually the first with gyrostabilization but it was disabled by the crew because it was difficult to load while on the move or some such reason.

According to Zaloga & Grandsen, the T-26S model 1937 had single-axis stabilization, as did the T-28 1938 model for its main armament.

The Sherman was not even the first US production tank to be so equipped; both the Stuart (from mid-1941) and the Lee had stabilizers.

All the best,

John.

(Edited because I munged up James Grandsen's name)

[ June 25, 2006, 05:24 AM: Message edited by: John D Salt ]

[c3k]

Hmmm,

Isn't the Abram's penetrator in the 10kg range? (Questioning the 125mm bore, 3.6kg, in the earlier post; 120mm, 10kg after sabot separation.)

Regards,

Ken

[John D Salt]

Originally posted by c3k:

Isn't the Abram's penetrator in the 10kg range? (Questioning the 125mm bore, 3.6kg, in the earlier post; 120mm, 10kg after sabot separation.)

Hey, I didn't bother to do any more research than a rough estimate demanded. I just googled "125mm muzzle velocity", and the first hit was

http://en.wikipedia.org/wiki/125_mm_smoothbore_rounds

which looked good enough to me. I'll try re-running the calculator with a 4.5Kg penetrator, but I don't expect it will make a blind bit of difference.

All the best,

John.

[John D Salt]

Originally posted by John D Salt:

I'll try re-running the calculator with a 4.5Kg penetrator, but I don't expect it will make a blind bit of difference.

It appears to make no difference at all in the case of 2% ranging error, but with 20% a 4.9Kg penetrator adds at most 1, and a 10Kg penetrator at most 3, percentage points to the P(hit) at the most sensitive ranges (1200 to 1300 metres). So I hardly think it matters.

All the best,

John.

[John Kettler]

John D Salt,

Who or what, praytell, is Joad? Anything like JMEM?

Regards,

John Kettler

[John D Salt]

Originally posted by John Kettler:

Who or what, praytell, is Joad? Anything like JMEM?

C E M (Cyril) Joad, philosopher and Brains Trust panellist, whose catchphrase was "It all depends on what you mean by..."

http://en.wikipedia.org/wiki/C._E._M._Joad

All the best,

John.

[mav1]

Thanks for the info John D Salt.

So which tank was the first to have a laser rangefinder?

[John D Salt]

Originally posted by mav1:

Thanks for the info John D Salt.

So which tank was the first to have a laser rangefinder?

I believe (staring at pages 135 to 136 of the International Defence Review special issue on Main Battle Tanks, 1976) that the first vehicle in service with a laser range-finder was the M60A2, originally designated M60A1E2. This was produced by the Hughes Aircraft Company, which had been experimenting with laser range-finders since the Colidar Mk 1 in 1961. The M60A2 especially needed good rangefinding for the low-velocity 152mm round fired by its Shillelagh gun/missile system. The same system was fitted in the M551 Sheridan, which also needed a laser range-finder. The orders for these were completed in 1970 and 1971 respectively. Neither vehicle was successful in service, largely because of difficulties with the Shillelagh system.

The first "real" gun tanks in service with laser range-finders were I believe the Chieftain Mk 3/3, equipped with a Barr & Stroud laser range-finder, and the STRV 103 ("S" tank), with one developed by Jungner Instrument AB.

Shortly thereafter the Cobelda system, developed by SABCA in Belgium, was adopted for Belgian Army and later Australian Arrmy Leopards. Both the Barr & Stroud and SABCA units were developed under licence from Hughes. The original Hughes family of range-finders used pink ruby lasers, but the STRV 103's sytem and contemporary designs by CILAS of France and Marconi Radar Systems used neodymium-doped glass. Later systems used neodymium-YAG lasers and CO2 lasers.

All the best,

John.

[Wicky]

Plus as a spin off from military developments, lasers perform a marvellous job in Ophthalmology.

i.e. YAG Laser Peripheral Irodotomy (LPI)

A different type of laser, known commonly as a YAG laser, is used in several different treatments of the eye. The YAG laser is different from the argon laser in that it doesn't coagulate or burn tissue. It actually disrupts tissue which allows the physician to create openings in the tissue. The procedure known as a laser peripheral iridotomy (LPI) is used to treat acute and chronic angle closure glaucoma. The YAG laser is used to create a hole in the iris (an iridotomy) which thus allows a new passage for the fluid in the eye to exit out of the eye. In angle closure glaucoma, the fluid is blocked from exiting the eye and the iridotomy thus, relieves this blockage. In acute angle closure glaucoma, this can often save the vision in the eye if done soon enough. Prior to the development of this procedure, the patient with angle closure glaucoma would need to go through a risky surgical procedure in order to treat this disorder.

Also lasers are used for treating Diabetics' retinas and treating a complication following cataract replacement lens implants.

[Michael Emrys]

Originally posted by Wicky:

Plus as a spin off from military developments, lasers perform a marvellous job in Ophthalmology.

i.e. YAG Laser Peripheral Irodotomy (LPI)

Just had that done a week ago. Second time in a year. Hope it works this time.

Michael

[John Kettler]

John D Salt,

Learned something new! Thanks! The entry itself in Wiki could use some work, for I see "physical" appearing where the word clearly intended is either "psychic" or "psychical," and some sentences are verb free.

As for the LRF, in the Shillelagh gun/missile system, the gun side of the equation was way too powerful for a lightweight aluminum tank, decollimating the Shillelagh guidance optics (IR beamrider) with but a single firing of the gun proper. This was reported in ARMOR magazine, but I am personally unaware that it was an issue with the much heavier M60A1E2/M60A2, which could handle the whopping recoil forces the gun generated.

Wicky,

And YAG LPI makes another!

Regards,

John Kettler

[MikeyD]

"Isn't the Abram's penetrator in the 10kg range?"

The Abrams penetrator would be DU of course (heavier than lead). Also, i've seen photos of the 120mm penetrators and they appear to have a substantially thickened middle so they're not quite classic arrow-shaped anymore. Maybe that was to reduce the likeylhood of a very long rod snapping on impact? I could imagine them weighing twice as much as a classic tungsten arrow projectile.

[c3k]

MikeyD,

Yes, quite right. I posted the 10kg figure to bring the higher mass to John D. Salt's attention, not to try to prove that he was wrong. I do find it interesting that the smaller bore 120mm gun fires a higher mass penetrator than the 125mm gun. Any idea on the 125mm muzzle velocity?

Thanks,

Ken

[MikeyD]

Talk about higher-mass penetrators, I undertand the original (and still in service ouside Russia?) 125mm Russian dart wasn't even tungsten but good-old steel! Basically, the round was designed to meet a specific target (possibly piercing a Centurion a 1000m?) and not a penny extra spent for added performance.

John D Salt's number of 1800ms sounds somewhat familiar mv-wise for the 125mm gun.

[KG_Brandenburg]

First time on this forum... Hi all:)

Id just like to comment on the reason that the soviets used steel penetrators. The real reason was simple economics. Im at school and dont have my books handy but I rememberewd reading a book that touched on this subject a bit...

The russians had a large tank force and needed alot of shells. Steel was by far the most abundant resource available and therefore the most cost effective..

Branden

[Jeff Duquette]

Originally posted by John D Salt:

I believe that the calibre, mass and velocity figures are reasonable for a 125mm projectile, the muzzle dispersion is a SWAG but I should think of the right order.[/QB]

Hi John:

Inherent dispersion for most NATO APFSDS typically runs around 0.2mils in both the vertical and horizontal planes. This is only shot-to-shot dispersion.

Best Regards

JDuquette

[John D Salt]

Originally posted by Jeff Duquette:

[snips]

Inherent dispersion for most NATO APFSDS typically runs around 0.2mils in both the vertical and horizontal planes. This is only shot-to-shot dispersion.

Interesting -- is there a good published source for this?

That is, of course, and extemely high degree of accuracy, and I assume due to having ESR gun barrels, muzzle reference systems and all the rest of the modern gubbins. I doubt that a Soviet 125mm of 1962 vintage could match that -- indeed, I doubt that any NATO guns of that vintage could.

Still, even if we credit the 125mm with a dispersion at the muzzle of 0.2 mil, the difference between P(hit) with a rangefinder and without seems to remain pretty huge once one gets to 1000 metres -- as you'd probably expect.

I've extended the steam-powered P(hit) device to 3000 metres, and get the following P(hit) figures for a projectile 44mm in diameter and 3.6Kg in mass with a 1800 m/sec m.v., against a static 2.5 x 2.5m target:

With ranging error of 2 %

500m___1000m___1500m___2000m___2500m___3000m

100%___100%____100%_____96%_____67%_____39%

With ranging error of 20 %

500m___1000m___1500m___2000m___2500m___3000m

100%____94%_____40%_____16%______7%______4%

Even with very high velocity, flat-trajectory guns with very low muzzle dispersion, rangefinding error is critical above about a kilometre.

All the best,

John.

[Jeff Duquette]

Originally posted by John D Salt:

Interesting -- is there a good published source for this?

That is, of course, and extemely high degree of accuracy, and I assume due to having ESR gun barrels, muzzle reference systems and all the rest of the modern gubbins. I doubt that a Soviet 125mm of 1962 vintage could match that -- indeed, I doubt that any NATO guns of that vintage could.

Firing tables (range tables for you UK folks) are the best source. Don't know about early Soviet APFSDS aside from 100mm BM1 & BM2. But than no Soviet tank was sporting a 125mm smooth-bore in 1962.

As to NATO guns of 1962 vintage, nobody in NATO had an in service APFSDS round at that time. The closest thing would be APDS. The 50% Zone for 105mm L7 gun firing L28A1 APDS (or the M68 gun firing M392A1) was 0.24-mils in height and width\breadth. See War Office Publication dated 5th October 1960, "Range Table for Gun, 105mm Tk. L7A1, Shot, 105mm APDS".

I suppose I would need to understand what you are referring to by "muzzle dispersion". Usually shot-to-shot dispersion is presented in terms of probable error or dispersion probability zones –Like a 50% Zone, or 90% Zone. When you say "muzzle dispersion", are you talking about shot-to-shot systematic dispersion? In addition, when you say 1-mil of "muzzle dispersion" are you intending this figure to represent a specific dispersion probability zone?

Regards

JD

[John D Salt]

Originally posted by Jeff Duquette:

[snips]

But than no Soviet tank was sporting a 125mm smooth-bore in 1962.

I was just going by the date of introduction in the Wikipedia article and Vasily Fofanov's site at

http://armor.kiev.ua/fofanov/Tanks/

...which, I notice, gives a 0.25 mil figure for "maximum dispersion" of 125mm fin rounds. I don't pretend to understand where he got 1962 from -- elesewhere onm the site he gives the date of introduction of the 125mm gun on the T-64A as 1969.

Originally posted by Jeff Duquette:

The 50% Zone for 105mm L7 gun firing L28A1 APDS (or the M68 gun firing M392A1) was 0.24-mils in height and width\breadth. See War Office Publication dated 5th October 1960, "Range Table for Gun, 105mm Tk. L7A1, Shot, 105mm APDS".

Unfortunately that doesn't seem to be held at the PRO. Indeed if the catalogie is to be trusted, their collection of such stuff appears pretty thin. Maybe I should pottle over to Bovington and ransack their library...

Originally posted by Jeff Duquette:

I suppose I would need to understand what you are referring to by "muzzle dispersion". Usually shot-to-shot dispersion is presented in terms of probable error or dispersion probability zones –Like a 50% Zone, or 90% Zone. When you say "muzzle dispersion", are you talking about shot-to-shot systematic dispersion?

Yup. Although as this is the only source of error I'm considering apart from range estimation and laying error due to target motion, it could be held to include all sorts of things in the error budget apart from the ballistic characteristics of the gun, such as sight collimation error, trunnion tilt and so on.

Originally posted by Jeff Duquette:

In addition, when you say 1-mil of "muzzle dispersion" are you intending this figure to represent a specific dispersion probability zone?

Sorry, I should have made this clear, I mean the standard deviation. I am using the method of calculating P(hit) described in "Applied operations research: Examples from defence assessment", by R W Shephard, D A Hartley, P J Haysman, L Thorpe & M R Bathe, Plenum Press, 1988.

I understand that the rule of thumb to get from 50% zones to s.d.s is to multiply by 0.74, so the errors apparently applicable for the 105mm L7 strike me as very small indeed.

All the best,

John.